1. Field of the Invention
The present invention relates to a chemical composition which, when applied to growing plants, is effective in stimulating plant growth. More particularly, the present invention relates to a chemical formulation of 1-triacontanol in combination with a polar organic solvent, metal ions, and water.
2. Description of the Prior Art
Recently, 1-triacontanol, CH.sub.3 (CH.sub.2).sub.28 CH.sub.2 OH, has been under investigation as a naturally-occurring plant growth stimulant (see Ries, et al., Science, 195:1339 (1977)). In fact, field trials and greenhouse trials are presently being conducted in order to optimize the conditions under which 1-triacontanol formulations can be effectively applied to plant life in order to obtain consistent increases in growth and crop yields.
In the research that is presently being conducted widely, utilizing 1-triacontanol as a plant growth stimulant, use is being made of relatively large quantities of surfactants in the chemical formulations in an attempt to disperse the 1-triacontanol effectively in water. Of course, the use of large amounts of water is essential in order to economically and effectively apply the chemical formulation to large areas of growing plants. Accordingly, it is imperative to render the 1-triacontanol water-soluble so that it may properly be applied using large amounts of water to plant life. However, the organic solvents which are presently being utilized to aid in emulsification of 1-triacontanol in water, for example, the use of chloroform or other water-insoluble solvents, along with surfactant additives, tend to be detrimental to plant life and to the environment. Thus, surfactants can hinder the entry of triacontanol into plants, rendering the effects of the compound ineffective.
During the course of research leading to the present invention, it has been discovered, surprisingly, that auxins and other plant growth substances alter the effects of 1-triacontanol. More specifically, the naturally-occurring auxin, indole-3-acetic acid (IAA) has been found to counteract any growth-promoting effect of 1-triacontanol. Auxins and 1-triacontanol are normally considered plant growth stimulating agents, and the investigation into the inhibitory interaction between the two substances led to the discovery that metal ions having a positive valence of +2 or more not only reverse the inhibition, but have an unexpected synergistic effect on the growth-stimulating effect of 1-triacontanol. Furthermore, this effect occurs in the presence of free metal ions which are not complexed or chelated. For example, the addition of surfactants such as Tweens, which effectively complex the metal ions, show either a decrease in plant growth when combined with 1-triacontanol formulations containing metal ions or show no effect at all. This same effect may be observed using the formulations disclosed in the U.S. Pat. No. 4,169,716 by Ashmead which teaches that 1-triacontanol may show a synergistic effect when combined with certain metal proteinates and a variety of other plant growth substances. These complexed proteinates (metal ions chelated with amino acids and peptides), therefore, are not considered to be within the scope of the present invention. Also, these complexes, together with those disclosed in U.S. Pat. No. 4,169,717 by Ashmead, appear to show a much lesser effect than the formulations of the present invention, and are employed under hydroponic conditions which may include surfactant additives in the case where 1-triacontanol is added. U.S. Pat. No. 4,169,716, which employs 1-triacontanol in the case of hydroponically grown wheat, furthermore, does not utilize free metal ions, and, in fact, both of the above mentioned U.S. Patents advise against the use of said metal ions due to the plant's inability to absorb same. The best mode of the present invention involves foliar application of the formulations containing free metal ions.
Calcium and other metal ions having a valence of +2 or more are known to alter the effects of the five classes of plant hormones. These include auxins (indole-3-acetic acid (IAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), naphthalene acetic acid (NAA), indole-3-acetonitrile, indole-3-butyric acid, naphthalene acetamide, 2-methyl-1-naphthalene acetic acid, 2-methyl-1-naphthalene acetamide, 2,4-dichlorobenzoic acid, and other compounds or analogs which promote cell elongation and have an affinity for auxin receptors), gibberellins (gibberellic acid (GA.sub.3) or other gibberellins), cytokinins (such as kinetin (6-furfurylamino purine), dimethylallylaminopurine, methylamino purine, methylhydroxymethylallylamino purine, phenylpurine, benzylurine, N-ethylpurine, N-propylpurine, diphenylurea, etc.), ethylene, and abscisic (see Poovaiah and Leopold, Plant Physiol., 58:783 (1976)). The following cations have the ability to increase auxin binding to cell membranes and inhibit auxin-stimulated growth in the order: EQU La.sup.+3 &gt;Ba.sup.+2, Ca.sup.+2, Sr.sup.+2 &gt;Mg.sup.+2, Mn.sup.+2 &gt;&gt;Li.sup.+, Na.sup.+, K.sup.+
(Poovaiah and Leopold, Plant Physiol., 58:182 (1976)). These metal ions are contained in the well-known Hofmeister series.
Indole-3-acetic acid (IAA), the endogenous auxin which occurs widely in all plants, is known to rapidly stimulate cell elongation and enlargement, a process that involves loosening of the cell wall. IAA occurs primarily in esterified form, the myo-inosital ester comprising about fifty percent in corn (Zea mays). Only about one to ten percent of the relatively large amount of IAA in corn occurs as free IAA. Auxin binding to cell membranes is a reversible process with a K.sub.m between 10.sup.-6 and 5.times.10.sup.-5 M. There are apparently two binding sites for auxins. Site 1 binds both active and inactive auxin analogs while site 2 appear to be auxin specific. A wide variety of synthetic auxins (not naturally-occurring) show enhanced activity over the naturally-occurring auxin, IAA (for example NAA, 2,4-D, 2,4,5-T, etc.).
While the metal ions of the Hofmeister series having a valence of +2 or more are known to effect auxin binding and are very effective in producing a synergistic effect when combined with 1-triacontanol using the methods of the present invention, other metal ions such as zinc, lead, cadmium, etc. are effective and in some cases superior to the Hofmeister series metal ions. Since these other metal ions are useful and are not known to affect auxin binding, the synergistic effect observed in combination with 1-triacontanol may not be related to increased auxin binding. Furthermore, since the pH of the formulations of the present invention must be maintained over 7, auxin binding would necessarily be inhibited rather than promoted (see Plant Physiol., 59:357 1977)). Therefore, no explanation for the surprising synergistic effect of metal ions having a valence of +2 or more in the 1-triacontanol formulations is apparent.
Since surfactant additives or other additives which effectively complex the metal ions of the present invention may not be used in carrying out the best mode of the invention, research by the present inventor has led to the discovery that the incorporation of a polar organic solvent must be used. The polar organic solvent should be one in which 1-triacontanol is soluble to some extent, and also one that shows a solubility in water. Such solvents are disclosed in U.S. Ser. No. 47,696, filed June 12, 1979, and U.S. Ser. No. 146,005, filed May 2, 1980, both by the present inventor. The polar solvents of the present invention include, but are in no way limited to, water soluble ketones, alcohols, ethers, acids, amines, and dipolar aprotic solvents (such as dimethyl formamide, dimethyl sulfoxide (DMSO), and hexamethyl phosphoramide), and the like.
The use of such solvents does not conflict with uses in the prior art. For example, U.S. Pat. No. 4,150,970 by Ries, et al., mentions solvents in which 1-triacontanol is soluble, such as ethyl alcohol, however, the use of such solvents to form concentrated solutions to be diluted with relatively large amounts of water is not disclosed or implied. Also, the formulation used in the Patent by Ries, et al., namely a nonpolar solvent to form a concentrate which requires a surfactant to emulsify same, is shown by the present invention and related applications by the present inventor to be inferior to formulations containing a polar organic solvent. In the following description of the preferred mode of the invention it will become clear that the solutions containing a polar organic solvent show improved increases and reproducibility in plant growth stimulation when used in the 1-triacontanol formulations described therein.
U.S. Pat. No. 2,168,550, issued September, 1937 to Zimmerman, et al., discloses useful improvements in formulating auxins for use in promoting root growth. These include the use of alcohols (which are polar organic solvents) to aid in the solubility of the auxins. It should be noted that auxins are equally effective when formulated in a number of ways well known in the art, and the teachings of Zimmerman, et al., refer only to a convenient method of formulation of said auxins. The use of polar organic in the present invention, on the other hand, is required for the reproducibility of results and essential when the metal ions of the invention are incorporated into 1-triacontanol formulations to circumvent the necessity of having to add a metal-complexing surfactant additive to aid in emulsification when a nonpolar solvent is employed.
The disclosure by Ohlrogge in U.S. Pat. No. 4,230,485, issued Oct. 28, 1980, includes acetone (a polar organic solvent) to aid in the formulation of 1-triacontanol, however, this pertains only to the use of said formulation on field corn at a stage of application after tassel initiation. The disclosure is not within the scope of the present invention since it pertains to foliar application of a 1-triacontanol formulation at a stage of growth of field corn outside the scope of the present invention (preferably at the two to five leaf stage and before tassel initiation).
Other documents, such as U.S. Pat. No. 2,277,744 by Cupery, et al., Mar. 31, 1942, and U.S. Pat. No. 3,360,717 by Miller, Dec. 28, 1971, and a number of references covering the growth effects of metal ions on plant life and modes of application of various pesticides and plant growth substances show no reference to formulations of 1-triacontanol formulation or application, either with or without metal ion additives, are of no utility with regard to the present invention as a result of close inspection by the present inventor. The benefits and marked advantages over the prior art of the formulations of the present invention will become apparent in the following description.